As known to all, the industrial production of hydrogen peroxide by anthraquinone route is a cycle process, anthraquinones dissolved in organic solvent is hydrogenated into anthrahydroquinones in the presence of palladium catalyst, and then anthrahydroquinones are oxidized into anthraquinone peroxides using air or oxidizing atmosphere. The hydrogen peroxide solution and anthraquinone organic phase will be generated by extraction of anthraquinone peroxide by water. The anthraquinone solution related in the cycle of hydrogenation-oxidation-extraction is called working fluid in industry. Anthraquinones used are usually alkyl anthraquiliones, more frequently-used are 2-alkylanthraquinones, for example, 2-ethylanthraquinone, 2-amylanthraquinone, 2-butylanthraquinone and their 5,6,7,8-tetrahydro alkyl anthraquinone derivatives. The solution is usually binary solvent made of hydrocarbon solvent such as arene, alkane or cycloalkanes, and trioctyl phosphate, triethyl phosphate or methyl cyclohexanol acetate, for example, the binary solvent made of arene and trioctyl phosphate is more frequently-used.
During the process of hydrogenation reduction, the main reactions are the synthesis of anthrahydroquinone (AHQ) by reduction reaction of anthraquinone (AQ) (reaction 1) and the synthesis of tetrahydro anthrahydroquinones (THAHQ) by hydrogenation of anthraquinones (reaction 2), and the rate of the oxidation reaction of tetrahydro anthrahydroquinone to synthesize tetrahydroanthraquinone (THAQ) (reaction 7) is lower than the rate of the oxidation reaction of anthrahydroquinone (reaction 8). The higher the content of tetrahydro anthrahydroquinone is, the more the energy consumption of oxidation reaction process is, and the energy consumption content of the oxidation reaction process is higher than half of energy consumption of the whole cycle process. In industry, anthraquinone, anthrahydroquinone, tetrahydroanthraquinone and tetrahydroanthraquinone are effective anthraquinones in working fluid. In addition, the side reaction of hydrogenation of tetrahydro anthrahydroquinone might be proceeded to generate octahydroanthrahydroquinone (OHAHQ) (reaction 3), theoretically, octahydroanthrahydroquinone can be oxidized to generate peroxide, however, the oxidation rate is very slow and it doesn't have any industrial value at all. Therefore, octahydroanthrahydroquinone is viewed as degradation product.
The cycle of reduction and oxidation repeated and the degradation products including hydroxyl anthrone (e.g. oxanthrone (OAT) in reaction 4), anthrone (e.g. anthranone (AT) and bianthrone (DAT) in reaction 5), and anthrahydroquinone epoxides (THAQE) (reaction 6) are generated during side reaction.
The reactions and side reactions in the reductive reaction process are as follows:

The reactions and side reactions in the oxidation process are as follows:THAHQ+O2→THAQE+H2O  Reaction 6THAHQ+O2→THAQ+H2O2  Reaction 7AHQ+O2→AQ+H2O2  Reaction 8
During the productive cycle of hydrogen peroxide, useless degradation products generated in every cycle are limited in quantity. However, the accumulation of degradation products from many repeated cycles in the working fluid will reduce the concentration of the effective anthraquinones including anthraquinone and anthrahydroquinone in the working fluid which will cause many problems such as production efficiency. The working fluid should be regenerated to avoid the accumulation of such degradation products in it. The industrialized regenerating method in this field is contacting the working fluid with α-Al2O3 or γ-Al2O3 to transform the degradation products into effective anthraquinones. The alumina used as catalytic agent here is called activated alumina. For example, German Patent DE 1,273,499 described the process of transforming tetrahydroanthraquinone epoxides into tetrahydroanthraquinone by reducing action of tetrahydroanthrahydroquinone in the presence of basic alumina (reaction 9):

The regenerating process of working fluid mentioned in US statutory invention registration H1787 is contacting working fluid with γ-Al2O3 at the temperature of 50-100° C. before regenerated, 3 mol of tetrahydroanthraquinone are transformed into 1 mol of anthraquinone and 2 mol of anthrahydroquinone (reaction 10). In addition, it is also indicated that the transformation efficiency is low and there will be large amount of by-products generated because of immediate regeneration after reduction.

A regenerating method for working fluid used for the production of hydrogen peroxide was reported in Chinese patent CN1168654C. Alumina granular made by extrusion were used in this patent and alkali metals, alkaline-earth metals or rare earth elements were added into alumina. Preferably, the alumina had a granularity of no more than 3.5 mm and a specific surface area of no less than 50 m2/g.
Such measures above are conducted to raise the transformation efficiency of the degradation products in working fluid or to extend the life time of alumina to reduce the cost of alumina replacement. The deactivation reason of alumina used in the production process of hydrogen peroxide is the crystallization and precipitation of degradation products and polymers of the solvent ingredients which caused the decline of active surface area and the lost of alkaline composition in some techniques. In fact, the renewal period of activated alumina varies from several days to dozens of days according to different processes. The renewal of activated alumina is the focus of attention for the manufacturer of hydrogen peroxide. Firstly, the frequent renewal of activated alumina will raise the cost, and secondly, the deactivated alumina can't be disposed freely because it contains organics such as oxanthrone and so on which might cause the spread of pollution. However, there are few methods to deal with these problems and few patents that present the regenerating methods of deactivated alumina used in the production of hydrogen peroxide. French Patent Fr 1,304,901 presents the regenerating method of activated sodium silicoaluminate alumina firstly. In the first place, the activated alumina should be washed using suitable solvent at the temperature of 80° C. and then treated by the steam of 130° C. to remove the residual solvent, and at last, the catalytic agent will be heat-treated for more than 1 hour, more preferred 8-12 hours at 400-450° C. This processing method also has disadvantages: high contents of residual carbon and sulfur in the regenerated alumina. The content of sulfur which might poison palladium catalyst will be transferred from the regenerated alumina to the working fluid.
U.S. Pat. No. 4,351,820 presents the high-temperature regenerating method of is sodium silicoaluminate used for the production of hydrogen peroxide which has 55-63% of alumina, the method contains the steps comprising: adding the deactivated sodium silicoaluminate into the oven filled with oxidizing atmospheres at 650-700° C. and then the oven is heated to 700-850° C. The air and the deactivated sodium silicoaluminate are added continuously in the same direction by using gas external heating rotary kilns. This method needs additional heating energy to preheat gas and solid materials added into the oven and evaporation of a large number of water, and at last the combustion temperature of organics will be achieved therein. Although it will satisfy the requirements of repeated regeneration, the technical disadvantage of this method is the high cost.